Epitopic regions of pneumococcal surface protein A

ABSTRACT

Regions of the PspA protein of the R×1 strain of Streptococcus pneumoniae have been identified as containing protection-eliciting epitopes which are cross-reactive with PspAs of other S. pneumoniae strains and which is cross-protective. One region comprises the 68-amino acid sequence extending from amino acid residues 192 to 260 of the R×1 PspA strain while another region comprises the C-terminal amino acid sequence extending from amino acid residues 293 to 588 of the R×1 PspA strain.

This application is a continuation of application Ser. No. 08/319,795, filed Oct. 7, 1994, which is a continuation-in-part application of Ser. No. 08/246,636 filed on May 20, 1994, which is a continuation-in-part of application Ser. No. 08/048,896 filed Apr. 20, 1993 now abandoned, which is a continuation-in-part of application Ser. No. 07/835,698 filed Feb. 12, 1992 now abandoned and is a continuation-in-part of application Ser. No. 07/656,773 filed Feb. 15, 1991 which is now abandoned.

FIELD OF INVENTION

This invention relates to recognition of epitopic regions of pneumococcal surface protein A (PspA), the major virulence factor of Streptococcus pneumoniae.

BACKGROUND TO THE INVENTION

Streptococcus pneumoniae is an important cause of otitis media, meningitis, bacteremia and pneumonia. Despite the use of antibiotics and vaccines, the prevalence of pneumococcal infections has declined little over the last twenty-five years.

It is generally accepted that immunity to Streptococcus pneumoniae can be mediated by specific antibodies against the polysaccharide capsule of the pneumococcus. However, neonates and young children fail to make an immune response against polysaccharide antigens and can have repeated infections involving the same capsular serotype.

One approach to immunizing infants against a number of encapsulated bacteria is to conjugate the capsular polysaccharide antigens to proteins to make them immunogenic. This approach has been successful, for example, with Haemophilus influenzae b (see U.S. Pat. No. 4,496,538 to Gordon and U.S. Pat. No. 4,673,574 to Anderson). However, there are over eighty known capsular serotypes of S. pneumoniae of which twenty-three account for most of the disease. For a pneumococcal polysaccharide-protein conjugate to be successful, the capsular types responsible for most pneumococcal infections would have to be made adequately immunogenic. This approach may be difficult, because the twenty-three polysaccharides included in the presently-available vaccine are not all adequately immunogenic, even in adults. Furthermore, such a vaccine would probably be much more expensive to produce than any of the other childhood vaccines in routine use.

An alternative approach for protecting children, and also the elderly, from pneumococcal infection would be to identify protein antigens that could elicit protective immune responses. Such proteins may serve as a vaccine by themselves, may be used in conjunction with successful polysaccharide-protein conjugates, or as carriers for polysaccharides.

In McDaniel et al (I), J.Exp.Med. 160:386-397, 1984, there is described the production of hybridoma antibodies that recognize cell surface proteins on S. pneumoniae and protection of mice from infection with certain strains of encapsulated pneumococci by such antibodies. This surface protein antigen has been termed "pneumococcal surface protein A" or PspA for short.

In McDaniel et al (II), Microbial Pathogenesis 1:519-531, 1986, there are described studies on the characterization of the PspA. From the results of McDaniel (II), McDaniel (III), J.Exp. Med. 165:381-394, 1987, Waltman et al., Microb. Pathog. 8:61-69, 1990 and Crain et al., Infect. Immun. 58:3293-3299, 1990, it was also apparent that the PspAs of different strains frequently exhibit considerable diversity in terms of their epitopes, and apparent molecular weight.

In McDaniel et al (III), there is disclosed that immunization of X-linked immunodeficient (XID) mice with non-encapsulated pneumococci expressing PspA, but not isogenic pneumococci lacking PspA, protects mice from subsequent fatal infection with pneumococci.

In McDaniel et al (IV), Infect. Immun., 59:222-228, 1991, there is described immunization of mice with a recombinant full length fragment of PspA that is able to elicit protection against pneumococcal strains of capsular types 6A and 3.

In Crain et al, (supra) there is described a rabbit antiserum that detects PspA in 100% (n=95) of clinical and laboratory isolates of strains of S. pneumoniae. When reacted with seven monoclonal antibodies to PspA, fifty-seven S. pneumoniae isolates exhibited thirty-one different patterns of reactivity. Accordingly, although a large number of serologically-different PspAs exist, there are extensive cross-reactions between PspAs.

The PspA protein type is independent of capsular type. It would seem that genetic mutation or exchange in the environment has allowed for the development of a large pool of strains which are highly diverse with respect to capsule, PspA, and possibly other molecules with variable structures. Variability of PspA's from different strains also is evident in their molecular weights, which range from 67 to 99 kD. The observed differences are stably inherited and are not the result of protein degradation.

Immunization with a partially purified PspA from a recombinant λ gtll clone, elicited protection against challenge with several S. pneumoniae strains representing different capsular and PspA types, as described in McDaniel et al (IV), Infect. Immun. 59:222-228, 1991. Although clones expressing PspA were constructed according to that paper, the product was unstable and isolation from cell fragments following lysis was not effected.

While the protein is variable in structure between different pneumococcal strains, numerous cross-reactions exist between all PspA's, suggesting that sufficient common epitopes may be present to allow a single PspA or at least a small number of PspA's to elicit protection against a large number of S. pneumoniae strains.

In addition to the published literature specifically referred to above, the inventors, in conjunction with co-workers, have published further details concerning PspA's, as follows:

1. Abstracts of 89th Annual Meeting of the American Society for Microbiology, p. 125, item D-257, May 1989;

2. Abstracts of 90th Annual Meeting of the American Society for Microbiology, p. 98, item D-106, May 1990;

3. Abstracts of 3rd International ASM Conference on Streptococcal Genetics, p. 11, item 12, June 1990;

4. Talkington et al, Infect. Immun. 59:1285-1289, 1991;

5. Yother et al (I), J. Bacteriol. 174:601-609, 1992;

6. Yother et al (II), J. Bacteriol. 174:610-618, 1992; and

7. McDaniel et al (V), Microbiol Pathogenesis, 13:261-268, 1992.

In the aforementioned copending U.S. patent applications Ser. Nos. 656,773 and 835,698 (corresponding to published International patent application, WO 92/1448), as well as in Yother et al (I) and (II), the disclosures of which are incorporated herein by reference, there are described the preparation of mutants of S. pneumomiae that secrete an immunogenic truncated form of the PspA protein, and the isolation and purification of the secreted protein. The truncated form of PspA was found to be immunoprotective and to contain the protective epitopes of PspA. The PspA protein described therein is soluble in physiologic solution and lacks at least the functional cell membrane anchor region.

The aforementioned USSNs' also describe characteristics of the mature R×1 PspA protein. The mature protein is composed of 588 amino acids and has a molecular weight of 65 kD. The N-terminal 288 amino acids are highly charged and predict an α-helical coiled-coil protein structure. The C-terminal 217 amino acids contain the surface anchor of PspA and does not appear to be α-helical. In the middle of the molecule is a proline rich region that is thought to traverse the cell wall.

In the specification which follows and the drawings accompanying the same, there are utilized certain accepted abbreviations with respect to the amino acids represented thereby. The following Table I identifies those abbreviations:

                  TABLE I                                                          ______________________________________                                         AMINO ACID ABBREVIATIONS                                                       ______________________________________                                                   A = Ala = Alanine                                                              C = Cys = Cysteine                                                             D = Asp = Aspartic Acid                                                        E = Glu = Glutamic Acid                                                        F = Phe = Phenylalanine                                                        G = Gly = Glycine                                                              H = His = Histidine                                                            I = Ile = Isoleucine                                                           K = Lys = Lysine                                                               L = Leu = Leucine                                                              M = Met = Methionine                                                           N = Asn = Asparagine                                                           P = Pro = Proline                                                              Q = Gln = Glutamine                                                            R = Arg = Arginine                                                             S = Ser = Serine                                                               T = Thr = Threonine                                                            V = Val = Valine                                                               W = Try = Tryptophan                                                           Y = Tyr = Tyrosine                                                   ______________________________________                                    

SUMMARY OF INVENTION

In accordance with the present invention, there has been identified a 68-amino acid region of PspA from the R×1 strain of Streptococcus pneumoniae which not only contains protection-eliciting epitopes, but also is sufficiently cross-reactive with other PspA's from other S. pneumoniae strains so as to be a suitable candidate for the region of PspA to be incorporated into a recombinant PspA vaccine.

The 68-amino acid sequence extends from amino acid residues 192 to 260 of the R×1 PspA protein. While the disclosure herein refers specifically to the specific 68 amino acid sequence of the R×1 PspA protein, any region of a PspA protein from any other S. pneumoniae species which is effectively homologous, as defined herein, to this sequence of the R×1 PspA protein is included within the scope of the invention, for example, from strains D39 and R36A.

Accordingly, in one aspect, the present invention provides an isolated PspA protein fragment comprising amino acid residues 192 to 260 of the PspA protein of the R×1 strain of Streptococcus pneumoniae and containing at least one protection-eliciting epitope, and optionally up to a further 40 residues of the protein in the NH2-terminal direction and/or the COOH-terminal direction, or being effectively homologous to such a fragment.

The protein fragment may be one containing an amino acid sequence corresponding to or effectively homologous to the amino acid residues 192 to 260 of the PspA protein of the R×1 strain and hence may comprise fragments larger or smaller than ones containing the specific amino acid sequence.

In accordance with another aspect of the present invention, an isolated PspA fragment is provided having an amino acid sequence encoded by pneumococcal DNA amplified by polymerase chain reaction (PCR) by oligonucleotide primers LSM4 and LSM6, as identified in Table III below. This pair of primers is capable of effecting PCR amplification of pneumococcal DNA from a number of strains of S. pneumoniae.

The protein fragment of the invention may be produced recombinantly in the form of a truncated C-terminal deleted product containing the protein fragment, specifically a truncated C-terminal-deleted product containing the approximately C-terminal third of an α-helical region of the native PspA protein, which may be the R×1 PspA.

The present invention also includes an isolated protein fragment comprising an amino acid sequence corresponding to that of a protein-eliciting epitope contained in amino acid residues 192 to 260 of the PspA protein of the R×1 strain of Streptococcus pneumoniae.

The amino acid sequence of the protein fragment need not be that found in strain R×1 but can be based on a corresponding sequence from another strain. Thus, the present invention also includes an isolated protein fragment comprising an amino acid sequence corresponding to that of amino acid residues 192 to 260 of the PspA protein of the R×1 strain of Streptococcus pneumoniae.

In particular, the invention includes an isolated protein fragment comprising the amino acid sequence of or effectively homologous with that of a protection-eliciting epitope corresponding to an epitope contained in amino acid residues 192 to 260 of the pneumococcal surface protein A (PspA) protein of the R×1 strain of Streptococcus pneumoniae, and including no more than 40 additional amino acid residues in the NH₂ - and/or the COOH-terminal direction.

The term "effectively homologous" used herein means, in relation to an amino acid sequence effectively homologous to a defined sequence, that the said amino acid sequence may not be identical to said defined sequence but may be at least about 70 percent, more preferably about 80 percent, still more preferably about 90 percent identical, provided that the antigenic epitope or epitopes in said amino acid sequence have properties substantially the same as the corresponding epitopes in said defined sequence.

We have further found that a PspA fragment including C-terminal regions of the PspA also contains protection-eliciting epitopes. Accordingly, in a further aspect, the present invention provides an isolated pneumococcal surface protein A (PspA) fragment comprising a C-terminal portion of the PspA protein from amino acid residue 192 and also a C-terminal portion of the PspA protein from amino acid residue 293, up to and including the amino acid residue 588 of the R×1 strain of Streptococcus pneumoniae and containing at least one protection-eliciting epitope and optionally up to a further 25 residues of the protein in the NH₂ -terminal direction, or being effectively homologous with such a protein fragment.

Further, an additional aspect of the present invention provides an isolated protein fragment comprising the amino acid sequence of or effectively homologous with that of at least one protection-eliciting epitope corresponding to an epitope contained in a C-terminal portion of the pneumococcal surface protein A (PspA) from amino acid residue 192 and contained in a C-terminal portion of the PspA protein from amino acid residue 293, up to and including amino acid residue 588 of the R×1 strain of Streptococcus pneumoniae, and including no more than 25 additional amino acid residues in the NH₂ -terminal direction.

Certain new monoclonal anti-PspA antibodies are described herein and, accordingly, in an additional aspect of the invention, there is provided a monoclonal anti-PspA antibody selected from those identified by the designations XiR 1526, XiR 35, XiR 1224, XiR 16, XiR 1325 and XiR 1323.

Certain oligonucleotide primers have been constructed for the amplification of pneumococcal DNA and, according to a further aspect of the invention, there is provided an oligonucleotide primer or probe which is LSM1, LSM2, LSM3, LSM4, LSM5, LSM6, LSM7, LSM8, LSM9, LSM10, LSM11, LSM12, LSM13, LSM14, LSM15, LSM16, LSM17 or LSM18, as identified in Table III below.

Pairs of such primers may be used for PCR amplification of pneumococcal DNA for the production of pneumococcal DNA or the detection of pneumococcal DNA in a sample, comprising a N-terminal primer selected from LSM1, LSM3, LSM4, LSM5, LSM7, LSM8, LSM10, LSM12 and LSM13 and a C-terminal primer selected from LSM2, LSM6, LSM9, LSM11 and LSM14. FIG. 3 shows the location of the primers in relation to the PspA protein.

Specific pairs of such oligonucleotide primers may be employed to amplify certain regions of the pneumococcal DNA for cloning into an expression vector and expression of the PspA fragment encoded by the amplified DNA. As described below primer pair LSM3 and LSM2 may be used in the production of plasmid pBC207, primer pair LSM4 and LSM2 may be used in the production of plasmid pBC100, primer pair LSM7 and LSM2 may be used in the production of plasmid pBAR501, and primer pair LSM4 and LSM6 may be used in the production of plasmid pBAR416.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A-1C contains the DNA sequence for the pspA gene of the R×1 strain of S. pneumoniae (SEQ ID NO: 1) with the deduced amino acid sequence for the PspA protein (SEQ ID NO: 2);

FIG. 2 contains a schematic representation of the domains of mature PspA protein as well as identification of certain plasmids containing gene sequences coding for the full length protein (pKSD 1014), coding for specific segments of the N-terminal portion of the protein (pJY4284 or pJY4285, pJY4310, pJY4306), coding for specific sequences of the C-terminal region of the protein (pBC207, pBC100, pBAR501, pBAR714) and coding for specific intermediate regions of the protein (pBAR416, pBAR635);

FIG. 3 contains a schematic representation of the domains of mature PspA protein along with identification of the location of the PCR primer sequences identified herein;

FIG. 4 contains a schematic representation of the domains of the mature PspA protein and the general location of epitopes recognized by certain monoclonal antibodies; and

FIG. 5 is an immunoblot of PspA protein gene products produced by plasmids identified therein.

GENERAL DESCRIPTION OF INVENTION

As described in the prior U.S. patent applications referred to above (and in corresponding WO 92/1448) and in Yother et al (I) and (II), the pspA gene of strain R×1 encodes a 65 kDa molecule composed of 588 amino acids. The nucleotide sequence (SEQ ID No: 1) of the pspA gene and derived amino acid sequence (SEQ ID No: 2) are set forth in FIG. 1. The DNA sequence of the pspA gene is contained on a HindIII-KpnI fragment that is 2086 base pairs in length. The pspA gene itself represents 1985 base pairs of the fragment and comprises an initial region containing transcription and translation signals with translation starting at the ATG/met (nucleotide position 127, codon position -31), followed by a leader sequence extending from the ATG/met to GCA/ala (nucleotide position 217, codon -1). Mature PspA starts with the glu amino acid at nucleotide position 220 (codon +1) and ends at the translational stop TAA/OCH at nucleotide position 1954. This translational stop codon is followed by transcription termination signals.

The N-terminal half of the molecule is highly charged and its DNA sequence predicts an α-helical coiled-coil protein structure for this region (288 amino acids), as seen in FIG. 2. The C-terminal half of PspA, which is not α-helical, includes a proline-rich region (83 amino acids) and a repeat region containing the highly conserved twenty amino acid repeats, as well as a slightly hydrophobic sequence of 17 amino acids at the C-terminus. It is known that PspA is anchored to S. pneumoniae by its C-terminal half and it is likely that the proline-rich region serves to tangle the molecule in the cell wall. In addition, it is anticipated that the highly-charged α-helical region begins at the cell wall and extends into and possibly through the capsule. This model is supported by the observation that the α-helical domain contains all the surface exposed epitopes recognized by monoclonal antibodies (MAbs) reactive with PspA on the pneumococcal surfaces.

The PspA protein of S. pneumoniae strain R×1 has been mapped to locate protection-eliciting epitopes. Such mapping has been effected by employing antibodies to PspA protein and recombinant fragments of PspA. This mapping technique, described in detail in the Examples below, has identified an amino acid sequence corresponding to the C-terminal third of the α-helical region of PspA as containing protection-eliciting epitopes, specifically the amino acid residues 192 to 260 of the R×1 PspA protein. The amino acid sequence from residues 192 to 260 is the C-terminal third of the α-helical sequence, expected to be near the cell wall surface.

We have shown that a recombinant PspA fragment from R×1 consisting of amino acids 192 to 299 (produced by pBAR 416) elicits cross-protection against challenge by a number of different wild-type strains of S. pneumoniae. We have also amplified the DNA from sixteen out of sixteen pneumococcal strains using a pair of oligonucleotide primers LSM4 and LSM6 and cloned the amplified DNA of many of these strains.

In addition, recombinant PspA fragments from R×1 expressed from E. coli by pBC100 and consisting of amino acids 192 to 588, i.e. including the C-terminal anchor region, also elicited cross-protection against challenge by a number of wild-type strains of S. pneumoniae, showing the presence of protection-eliciting epitopes. Furthermore, recombinant PspA fragments from R×1 expressed from E. coli by pBAR501 and consisting of amino acids 293 to 588, i.e. consisting only of the prolines and repeats region elicited cross-protection against challenge by a number of wild-type strains of S. pneumoniae, showing the presence of protection-eliciting epitopes in this fragment.

Since the portion of the sequence from residues 192 to 260 contains only 68 amino acids, individual PspA protein fragments of this size may not be optimally antigenic. This difficulty is overcome by producing recombinant proteins containing tandem fragments of different PspAs expressed by gene fusions of the appropriate portions of several pspA genes.

Accordingly, in a further aspect of the invention, there is provided a PspA protein fragment comprising a plurality of conjugated molecules, each molecule comprising amino acid residues 192 to 260 of the PspA protein of the R×1 strain of Streptococcus pneumoniae and containing at least one protection-eliciting epitope, each molecule being derived from a different strain of S. pneumoniae.

Such tandem molecules can be engineered to maintain proper coiled-coil structure at the points of junction and to be large enough to be immunogenic and to express an array of protection-eliciting epitopes that may cross-react with a wide spectrum of PspAs. Alternatively, individual recombinantly-produced peptides may be attached by chemical means to form a complex molecule.

A further alternative is to attach the PspA fragment to a larger carrier protein or bacterial cell, either as a recombinant fusion product or through chemical attachment, such as by covalent or ionic attachment.

The protein fragments, as well as peptide analogs thereof, provided herein are useful components of a vaccine against disease caused by pneumococcal infection. Accordingly, the present invention provides, in a yet further aspect, an immunogenic composition comprising at least one PspA protein fragment as defined herein as an immunologically-active component thereof.

We have previously shown that, although PspAs are serologically variable, antisera raised against individual PspAs are sufficiently cross-reactive that they can frequently protect against S. pneumoniae which express serologically distinguishable PspAs. We have now shown herein that full-length PspAs from different pneumococcal strains, both from natural sources and produced recombinantly, can protect an animal model from challenge by different pneumococcal isolates. These results indicate that a limited number of serological PspA types may elicit protection against a broad spectrum of different pneumococci.

The immunogenic compositions, including vaccines, provided herein, comprising full-length PspA or the various PspA fragments described herein, elicit an immune response by the host to which it is administered including the production of antibodies by the host.

The immunogenic composition may be prepared as injectables, as liquid solutions or emulsions. The PspA or immunogenic fragment thereof may be mixed with physiologically acceptable carriers which are compatible with the PspA material. These carriers may include water, saline, dextrose, glycerol, ethanol and combinations thereof. The vaccine may further contain auxiliary substances, such as wetting or emulsifying agents, pH buffering agents, or adjuvants to further enhance the effectiveness of the vaccine. Vaccines may be administered by injection subcutaneously or intramuscularly.

Alternatively, the immunogenic compositions comprising full-length PspA or immunogenic fragments thereof formed according to the present invention, may be delivered in a manner to evoke an immune response at mucosal surfaces Thus, the immunogenic composition may be administered to mucosal surfaces by, for example, the nasal or oral (intragastric) routes. Alternatively, other modes of administration including suppositories may be desirable. For suppositories, binders and carriers may include, for example, polyalkylene glycols and triglycerides. oral formulations may include normally employed incipients, such as pharmaceutical grades of saccharine, cellulose and magnesium carbonate.

These immunogenic compositions may take the form of solutions, suspensions, tablets, pills, capsules, sustained release formulations or powders and contain 1 to 95% of the microparticles of the present invention.

The immunogenic compositions are administered in a manner compatible with the dosage formulation, and in such amount as to be therapeutically effective, protective and immunogenic. The quantity to be administered depends on the subject to be treated, including, for example, the capacity of the subject's immune system to synthesize antibodies, and if needed, to produce a cell-mediated immune response. Precise amounts of PspA and/or fragment thereof required to be administered depend on the judgement of the practitioner. However, suitable dosage ranges are readily determinable by one skilled in the art and may be of the order of micrograms to milligrams. Suitable regimes for initial administration and booster doses are also variable, but may include an initial administration followed by subsequent administrations. The dosage of the vaccine may also depend on the route of administration and will vary according to the size of the host.

Protein fragments according to the invention may be made in any desired manner. In particular, unique DNA probes may be tailored in known manner for use in a PCR reaction to amplify genomic DNA coding for a desired fragment, the amplified DNA is inserted into a suitable plasmid vector and the vector is utilized in a known manner to express the protein in a suitable host, such as E. coli, adopting, for example, the methods taught in Examples 2 and 3 below.

The appropriate PspA fragments may be cloned and expressed and their truncated products expressed under the control of an appropriate promoter, e.g. a vector containing the E. coli lac promoter expressing the E. coli ompA and leader sequence to create an ompa::pspA fusion plasmid. Optionally, the sequence coding for the PspA fragment may be linked to a sequence coding for a further protein suitable for injection into humans. Such proteins may be those already used as vaccines, because they are known to elicit protective immune responses and/or known to function as strong immunologic carriers. Such proteins may include the partial or complete amino acid sequence of toxins, such as tetanus toxin, or outer membrane proteins, such as that of group B subtype 2 Neisseria meningitis.

It is also possible to produce a fusion protein composed of the cross-reactive protection-eliciting regions of several different PspA molecules, as mentioned above. Such a fusion protein may be made large enough (≧240,000 molecular weight) to be highly immunogenic and as a single protein may elicit cross-protection to as many different pneumococci as possible. The combination of cross-protective 70 amino acid regions from 5 to 6 PspAs would be large enough to be highly immunogenic. Constructs expressing epitopes from more than one PspA are especially attractive since PspAs of pneumococci are known to differ serologically. Present evidence indicates that a widely protective vaccine will need to contain cross-reactive protection-eliciting epitopes from more than one different pneumococcus.

It is possible to design such a fusion protein so that it also carries a domain that would assist with isolation of the fusion product by including the choline binding region of PspA, or a ligand binding domain from other proteins, such as the maltose binding protein (encoded by malE) of E. coli. In the former case, the fusion protein may be isolated by adsorption to a choline Sepharose® column and elution using 2% choline chloride. In the latter case, adsorption is to a mannose-Sepharose column, followed by elution with a solution containing mannose.

In the construction of such a fusion protein containing tandem cross-reactive coiled-coil PspA regions, it is critical not only that the appropriate open reading frame of each down stream gene fragment be preserved at the junctions of the ligated gene fragments, but that the heptad motif of the coiled-coil amino acid sequence not be disrupted. One way to accomplish the latter is to construct the gene fusions so that they occur within naturally occurring non-coil-coiled regions found in the α-helical domain of PspA. In Yother et al (I), such non-coiled-coil breaks were identified at amino acid positions 169 to 176, 199, 225, 254, 274 and 289. Fusions between two or more cross-protedtive regions (residues 192-260) at or near positions 170 or 199 at one end and at or near residues 274 or 289 at the other end, can be expected to be able to express the epitopes normally expressed within the coiled-coil regions.

In each case, the simplest way to prepare such constructs is by PCR amplification of the DNA used to construct the gene fusions. In this way, it is possible to prepare the relevant sequence with appropriate restriction sites. The design of gene fusions and the PCR primers used to produce, the individual pspa fragments will be carried out so that the proper reading frame will be preserved in each fused gene fragment at the nucleotide level.

It is also possible to synthesize peptides according to the invention having the appropriate amino acid sequence by conventional peptide synthesis.

BIOLOGICAL MATERIALS

The Examples which follow as well as in the accompanying drawings, reference is made to certain plasmid materials containing whole or truncated pspA gene sequences. The following Table II provides a summary of such materials:

                  TABLE II                                                         ______________________________________                                         Plasmid    Identification                                                                               Gene Product                                          ______________________________________                                         pKSD1014   whole gene    amino acids 1 to 588                                  pJY4284 or 5' terminal region                                                                           amino acids 1 to 115                                  pJY4285                                                                        pJY4310    5'-terminal region                                                                           amino acids 1 to 192                                  pJY4306    5'-terminal region                                                                           amino acids 1 to 260                                  pBC207     3'-terminal region                                                                           amino acids 119 to 588                                pBC100     3'-terminal region                                                                           amino acids 192 to 588                                pBAR416    internal region                                                                              amino acids 192 to 299                                pBAR501    3'-terminal region                                                                           amino acids 293 to 588                                ______________________________________                                    

In addition, reference is made in the following Examples to certain PCR oligonucleotide primer sequences. Further, the present invention provides certain oligonucleotide primers useful, in combinations, for amplifying selected portions of pneumococcal DNA. In the following Table III is provided identification of the primer, description thereof, the 5' to 3' sequence of the primer and the nucleotide position of the primer sequence on the DNA of the R×1 strain of S. pneumoniae. FIG. 3 also shows the locations of primers LSM1 to LSM14 in relation to the domains of mature PspA protein.

                                      TABLE III                                    __________________________________________________________________________     PCR Oligonucleotde Primers                                                     Designation                                                                          Description   Seguence 5'-3'                                                                              SEQ ID NO.                                                                           Nucleotide Position                     __________________________________________________________________________     LSM1  in the 3' end of the prolines                                                                CCg gAT CCA gCT CCT                                                                          3    1312 to 1331                                  flanking the repeat region                                                                   gCA CCA AAA AC                                             LSM2  "The" 3' primer; covers the                                                                  gCg CgT CgA Cgg CTT                                                                          4    1990 to 1967                                  last 5 amino acids                                                                           AAA CCC ATT CAC CAT                                                            Tgg                                                        LSM3  within the α-helix                                                                     CCg gAT CCT gAg CCA                                                                          5    576 to 598                                                  gAg CAg TTg gCT g                                          LSM4  within the α-helix                                                                     CCg gAT CCg CTC AAA                                                                          6    792 to 814                                                  gAg ATT gAT gAg TCT g                                      LSM5  starts internal to "glu" the                                                                 gCg gAT CCC gTA gCC AgT                                                                      7    228 to 253                                    mature coding sequence                                                                       CAg TCT AAA gCT g                                          LSM6  at the 5' end of the prolines                                                                CTg AgT CgA CTg gAg TTT                                                                      8    1117 to 1093                                                CTg gAg CTg gAg C                                          LSM7  opposite orientation of LSM6                                                                 CCg gAT CCA gCT CCA                                                                          9    1093 to 1117                                                gCT CCA gAA ACT CCA g                                      LSM8  covers the -35 sequence                                                                      gCg gAT CCT TgA CCA                                                                         10    -79 to -56                                                  ATA TTT ACg gAg gAg gC                                                                            (47 to 70)                              LSM9  opposite orientation of LSM8                                                                 gTT TTT ggT gCA ggA gCT                                                                     11    1331 to 1312                                                gg                                                         LSM10 within the repeat region                                                                     gCT ATg gCT ACA ggT Tg                                                                      12    1441 to 1457                            LSM11 opposite orientation of LSM10                                                                CCA CCT gTA gCC ATA gC                                                                      13    1457 to 1441                            LSM12 in the leader peptide                                                                        CCg gAT CCA gCg TCg                                                                         14    161 to 187                                    sequence      CTA TCT TAg ggg CTg gTT                                    LSM13 at the HindIII site upstream                                                                 gCA AgC TTA TgA TAT                                                                         15     1 to 26                                      from the coding region region                                                                AgA AAT TTg TAA C                                          LSM14 opposite orientation of LSM4                                                                 gCg CgT CTC TTT gAg CTC                                                                     16    802 to 776                                                  TTg TTC TAg TCT                                            LSM15 (S)                                                                            LSM14 with a stop codon                                                                      CGC GTC GAC TCA GAG                                                                         17    793 to 781                                                  CTC TTG TTC TAG                                            LSM16 (S)                                                                            5' to LSM6 with a stop codon                                                                 CGC GTC GAC TCA CTC                                                                         18    1091 to 1069                                                ATT AAC TGC TTT                                            LSM17 LSM5 with a different reading                                                                gC ggA TCC CgT AgC CAg                                                                      19    228 to 253                                    frame         TCA gTC TAA AgC Tg                                         LSM18 LSM2 without a stop condon                                                                   TAT TTC AgT TAC ggT                                                                         20    1990 to 1955                                                TAC CAC TTA CCC TTA                                                            Agg Cg                                                     __________________________________________________________________________

EXAMPLES Example 1

This Example describes the bacterial strains, plasmids and monoclonal antibodies used herein, as well as the procedure for immunization of mice using the monoclonal antibodies.

S. pneumoniae strains, identified in Table III below, were grown in Todd Hewitt broth with 0.5% yeast extract at 37° C. or on blood agar plates containing 3% sheep blood in a candle jar. E. coli strain DH1 (Hanahan, J. Mol. Biol. 166:557) was grown in LB medium or minimal E medium. Plasmids included pUC18 (Gene 33:103), pJY4163 (Yother et al (II)), and pIN-III-ompA (EMBO J. 3:2437).

All antibody-secreting hybridoma lines were obtained by fusions with non-antibody-secreting myeloma cell line P3-X63-Ag.8.653 (J. Immunol. 123:1548). The specific antibodies employed are identified in Table IV below. The anti-PspA hybridoma cell lines Xi64, Xi126 and XiR278 have previously been described in McDaniel et al (I) and Crain et al (supra). The remaining cell lines were prepared by immunizing CBA/N mice with recombinant D39 PspA expressed in λgtII by the technique described in McDaniel et al (I). The cell lines producing antibodies to PspA were all identified using an ELISA in which microtitration plates were coated with heat-killed (60° C., 30 mins) S. pneumoniae R36A or R×1, which would select for those MAbs that react with surface exposed epitopes on PspA. The heavy chain isotypes of the MAbs were determined by developing the ELISA with affinity purified goat antibody specific for μ and γ heavy chains of IgM and IgG mouse immunoglobulin. The specificity of the MAbs for PspA was confirmed by immunoblot analysis.

All six newly-produced MAbs, identified in Table IV as XiR 1526, XiR 35, XiR 1224, XiR 16, XiR 1325 and XiR 1323, detected a protein of the expected size (apparent molecular weight of 84 kDa) in an immunoblot of strains R×1 and D39. No reactivity was observed for any of the MAbs in an immunoblot of strain WG44.1, a PspA variant of Rx1 (see McDaniel et al (III) and Yother et al (II)).

These six antibodies along with the previously described antibodies Xi64, Xi126 and XiR278, made up a panel one mice antibodies used to map epitopes on PspA, as described in Example 5 below.

                                      TABLE IV                                     __________________________________________________________________________     Renetivities of MAbs with PspAs from Streptococcus pneumoniae                                        Monoclonal Antibody (Isotype)                            Streptococcus pneumoniae                                                                             XIR1526                                                                             XIR35                                                                              XIR1224                                                                             XI126                                                                               XIR16                                                                              X164                                                                               XIR1325                                                                             XIR278                                                                             XIR1323              Strain Capsule type                                                                         PspA type                                                                           Ref. #                                                                             (IgG2b)                                                                             (IgG2a)                                                                            (IgM)                                                                               (IgG2b)                                                                             (IgG2a)                                                                            (IgM)                                                                              (IgG2a)                                                                             (IgGI)                                                                             (IgM)                __________________________________________________________________________     Rx1    rough 25   36  ++   ++  ++   ++   ++  ++  ++   ++  ++                   ATCC101813                                                                            3      3   37  -    -   -    ++   -   ++  ++   ++  ++                   EF10197                                                                               3     18   38  -    -   -    -    -   -   -/+  ++  -                    BG9739 4     26   38  -    -   -    -    -   -   ++   +   ++                   L81905 4     23   31  -    -   -    -    -   -   -    -   -                    BG-5-8A                                                                               6A     0   38  -    -   +    -/+  -   -   -    +   +                    BG9163 6B    21   38  -    -   -    -    -   -   -    +   -                    LM100  22    ND   --  -    -   -    -/+  -   -   -    -   -                    WU2    3      1   39  -    -   -    ++   -   ++  ++   ++  ++                   Protection against WU2                                                                               -    -   -    +    -   +   +    +   +                    __________________________________________________________________________

The protective capacity of the MAbs was tested by injecting CBA/N mice i.p. with 0.1 ml of 1/10 dilution (about 5 to 30 μg) of each MAb 1 hr prior to i.v. injection of 10³ CFU of WU2 or D39 pneumococci (>100×LD₅₀). Protection was judged as the ability to prevent death of all mice in a group. All non-protected mice died of pneumococcal infection within 48 hours post challenge.

Example 2

This Example describes the provision of the pspA gene from pneumococcal strain R×1 by polymerase chain reaction (PCR) and the procedure for immunization of mice by PspA fragments.

PCR primers were designed based on the sequence of the pspA gene from pneumococcal strain R×1 (see FIG. 1). The 5'-primers were LSM3, LSM4 and LSM7. LSM3 was 28 bases in length and started at base 576, LSM4 was 31 bases in length and started at base 792, and LSM7 was 31 bases in length and started at base 1093. All three primers contained an additional BamHI site. The 3' pspA primers were LSM2 which was 33 bases in length and started at base 1990 and LSM6 which was 31 bases in length and started at base 1117. Both primers LSM2 and LSM6 contained an additional SalI site. The nucleotide sequences for the primers are set forth in Table III above.

Primer pairs LSM3-LSM2 were used to generate pBC207, primer pairs LSM4-LSM2 were used to generate pBC100, primer pairs LSM7-LSM2 were used to generate pBAR501 and primer pairs LSM4-LSM6 were used to generate pBAR416, by the procedure generally outlined below.

Approximately 10 ng of genomic R×1 pneumococcal DNA was amplified using a 5' and 3' primer pair. The sample was brought to a total volume of 50 μl containing a final concentration of 50 mM KCl, 10 mM tris-HCl (pH 8.3), 1.5 mM MgCl₂, 0.001% gelatin, 0.5 mM each primer and 200 mM of each deoxynucleoside triphosphate and 2.5 U of Taq DNA polymerase. Following overlaying of the samples with 50 μl of mineral oil, the samples were denatured at 94° C. for 2 mins and then subjected to 10 cycles consisting of 1 min. at 94° C., 2 min. at 50° C. and 3 min. at 72° C., followed by another 20 cycles of 1 min. at 94° C., 2 min. at 60° C. and 3 min. at 72° C. After completion of the 30 cycles, the samples were held at 72° C. for an additional 5 min., prior to cooling to 4° C.

Using primers LSM4 and LSM6 following the procedure described above, it has been possible to amplify the corresponding region from sixteen out of sixteen different S. pneumoniae strains, namely D39, WU2, BG9739, L81905, DBL6A, DBL5, BG9163, A66, EF6796, BG7322, EF5668, BG7376, LM100, BG6796, BG5-8A and R36A. In addition, the amplified fragments of some of these strains have been cloned, namely D39, WU2, BG9739, DBL6A, DBL5, A66, EF5668, LM100 and R36A.

Example 3

This Example describes expression of truncated PspA molecules.

3'-deleted pspAs that express N-terminal fragments in E. coli and which secrete the same fragments from pneumococci were constructed as described in the aforementioned U.S. patent applications Ser. Nos. 835,698 and 656,773 (see also Yother et al (II), supra).

For expression of the internal fragment, BAR416, and the 5'-deleted pspA constructs, the secretion vector pIN-III-ompA was used. Amplified pspA fragments were digested with BamHI and SalI and ligated into the appropriately BamHI/SalI--digested pIN-III-ompA vector, providing the inserted fragment fused to the ompA leader sequence in frame and under control of the lac promoter. Transformants of E. coli DH1 were selected on minimal E medium supplemented with casamino acids (0.1%), glucose (0.2%) and thiamine (0.05 mM) with 50 μg/ml of ampicillin.

For induction of lac expression, bacteria were grown to an optical density of approximately 0.6 at 660 nm at 37° C. in minimal E medium and IPTG was added to a concentration of 2 mM. The cells were incubated for an additional two hours at 37° C., harvested and the periplasmic contents released by osmotic shock. An immunoblot of the truncated PspA proteins produced by the various plasmids is shown in FIG. 4.

By these procedures, there were provided, for the 3'-deleted pspAs, plasmids pJY4284, pJY4285, pJY4310 and pJY4306, the internal fragment, pBAR416 and for the 5'-deleted pspAs, plasmids pBC207, pBC100 and pBAR501. Plasmid pJY4284 and pJY4285 contain an insert of 564 base pairs, nucleotides 1 to 564 and encoded a predicted 18 kDa PspA C-terminal-deleted product corresponding to amino acids 1 to 115. Plasmid pJY4310 contains an insert of 795 base pairs, nucleotides 1 to 795 and encoded a predicted 21 kDa C-terminal-deleted product corresponding to amino acid 1 to 192. Plasmid pJY4306 contained an insert of 999 base pairs, nucleotides 1 to 999 and encoded a predicted 29 kDa C-terminal-deleted product corresponding to amino acids 1 to 260. Plasmid pBC100 contained an insert of 1199 base pairs, nucleotides 792 to 1990, and encoded a predicted 48 kDa PspA N-terminal deleted product containing amino acids 192 to 588. pBC207 contained an insert of 1415 base pairs, nucleotides 576 to 1990, and encoded a predicted 51 kDa PspA N-terminal deleted product containing amino acids 119 to 588. pBAR501 contained an insert of 903 base pairs, nucleotides 1093 to 1990, and encoded a predicted 32 kDa PspA N-terminal deleted product containing amino acids 293 to 588. Plasmid pBAR416 contained an insert of 326 base pairs, nucleotides 792 to 1117, and encoded a predicted 12 kDa PspA internal molecule containing amino acids 192 to 299.

The pspA gene sequences contained in these plasmids code for and express amino acids as identified in FIG. 2.

Immunization of CBA/N mice with PspA fragments produced from the plasmids described in this Example was effected by subcutaneous injection in the subinguinal area with an osmotic preparation of the PspA fragment emulsified 1:1 in Complete Freund's Adjuvant (CFA). After 14 days, the mice were injected intraperitoneally with antigen diluted 1:1 in Ringer's lactate without CFA. Seven days later, the mice were challenged intravenously with at least 100 times the LD₅₀ of pneumococcal strain D39 or WU2. The survival of mice was monitored for 10 days.

Example 4

This Example describes the procedure of effecting immunoassays.

Immunoblot analysis was carried out as described in McDaniel et al (IV). The truncated PspA molecules prepared as described in Example 3 or pneumococcal preparations enriched for PspA (as described in McDaniel et al (II)) were electrophoresed in a 10% sodium dodecyl sulfate polyacrylamide gel (SDS-PAGE) and electroblotted onto nitrocellulose. The blots were probed with individual MAbs, prepared as described in Example 1.

A direct binding ELISA procedure was used to quantitatively confirm reactivities observed by immunoblotting. In this procedure, osmotic shock preparations were diluted to a total protein concentration of 3 μg/ml in phosphate buffered saline (PBS) and 100 μl was added to wells of Immulon 4 microtitration plates. After blocking with 1% bovine serum albumin in PBS, unfractionated tissue culture supernates of individual MAbs were titered in duplicate by 3-fold serial dilution through 7 wells and developed as described in McDaniel et al (IV) using a goat anti-mouse immunoglobulin alkaline phosphate conjugated secondary antibody and alkaline phosphate substrate. Plates were read in a DYNATECH (Trademark) plate reader at 405 nm, and the 30% end point was calculated for each antibody with each preparation.

Example 5

This Example describes mapping of the epitopes on PspA using the monoclonal antibodies prepared as described in Example 1.

The six newly-produced monoclonal antibodies described in Example 1 and identified in Table IV were used along with the previously-described monoclonal antibodies Xi64, Xi126 and XiR278 to map epitopes on PspA.

The reactivity of the MAb was determined by two methods. In one method, reactivity between the fragments and MAb was evaluated in immunoblots of the fragment preparations after they had been separated by SDS-PAGE. In the second method, a direct ELISA was used to quantify the reactivity of the MAbs with non-denatured PspA fragment.

To determine whether each of the MAbs recognized different epitopes, each of them was reacted with eight additional S. pneumoniae strains, as identified in Table IV, in immunoblots of SDS-PAGE separated proteins. Seven different patterns of activity were observed. Three antibodies, XiR16, XiR35 and XiR1526, appeared to recognize epitopes found on R×1 PspA but none of the other PspAs. Accordingly, it was possible that these three antibodies might all react with the same epitope as R×1 PspA.

MAb Xi64 and Xi126 both reacted strongly only with epitopes on ATCC 101813, WU2 and R×1 PspAs, but not with PspAs of the other strains. However, it is known from studies of larger panels of PspAs (as described in McDaniel et al (III) and Crain et al) that Xi126 and Xi64 recognize different determinants.

The remaining four antibodies each exhibited unique patterns of reactivity with the panel of PspAs. Accordingly, the nine antibodies tested recognized at least seven different epitopes on PspA.

For reasons which are not clear, the type 2 strain D39 appeared to be uniquely able to resist the protective effects of antibodies to PspA (McDaniel et al (IV)). As described in McDaniel et al (I), greater than forty times the amount of Xi126 was required to passively protect against the D39 strain as compared to the WU2 strain. None of the six newly-produced monoclonal antibodies protected against the D39 strain. In contrast, immunization of mice with R×1 PspA elicits protection against A66, WU2 and EF6796 strains (mouse virulent pneumococci of capsular types 3, 3 and 6A respectively), all of which have PspA types that are different from those of R×1 and D39 (see McDaniel et al (IV)). In view of the close serologic similarity between the type 25 PspA of R×1 and type 1 PspA of WU2 (Crain et al), WU2 pneumococci were used to challenge mice that had been passively protected with the MAbs. All five of the MAbs that were observed to bind WU2 PspA were able to protect against infection with 1000 CFU of WU2. Protective antibodies were found in IgM, IgG1, IgG2b and Ig2a heavy chain isotype classes.

The results are given in the following Table V:

                                      TABLE V                                      __________________________________________________________________________     Immunoblot reactivities of monoclonal antibodies with PspA                     from Strepococcus pneumoniae strains Rx1.sup.a and WU2.sup.b                               Monoclonal antibody                                                            (isotype)                                                          Streptococcus pneumoniae                                                                   XiR1526                                                                             XiR35                                                                              XiR1224                                                                             Xi126                                                                              XiR16                                                                              Xi64                                                                              XiR1325                                                                             XiR278                                                                             XiR1323                          Strain                                                                              PspA type                                                                             (IgG.sub.2b)                                                                        (IgG.sub.2a)                                                                       (IgM)                                                                               (IgG.sub.2b)                                                                       (IgG.sub.2a)                                                                       (IgM)                                                                             (IgG.sub.2a)                                                                        (IgG.sub.I)                                                                        (IgM)                            __________________________________________________________________________     Rx1.sup.a                                                                           25     +    +   +    +   +   +  +    +   +                                WU2.sup.b                                                                            1     -    -   -    +   -   +  +    +   +                                Protection against WU2                                                                     0/2  0/2 0/2  10/0                                                                               0/2 10/0                                                                              8/0  10/0                                                                               2/0                              infection.sup.c                                                                __________________________________________________________________________      .sup.a Rx1 is an nonencapsulated avirulent laboratory strain.                  .sup.b WU2 is a mousevirulent capsular type 3 strain.                          .sup.c Mice were given antibody intraperitoneally one hour before              intravenous challenge with 100 × ID.sub.50 of WU2.                       The results are expressed as number of mice alive/number of mice dead          after 14 days. Thirty control mice did not receive antibody and only one       survived challenge with WU2.                                             

Example 6

This Example describes mapping of the epitopes of PspA using the recombinant truncated PspA molecules formed in Example 3.

The five-overlapping C-terminal or N-terminal deleted PspA fragments, prepared as described in Example 3 and shown in FIG. 2, were used to map epitopes on PspA. The general location of the epitopes detected by each of the mice MAbs, as described in Example 5, was determined using five C-terminal-deleted and two N-terminal deleted PspA molecules. As a positive control, the reactivity of each antibody was examined with a clone, pKSD1014, expressing full-length PspA. As a negative control, the vector pIN-III-ompA was used.

The reactivities observed and the quantification of such activity is set forth in the following Table VI:

                                      TABLE VI                                     __________________________________________________________________________     Reactivity of PspA Fragments with Monoclonal Antibodies.sup.1                  PspA  Monoclonal Antibodies                                                    Fragments.sup.(2)                                                                    Xi126 XiR35                                                                               XiR1526                                                                             XiR1224                                                                             XiR16 XiR1323                                                                             Xi64 XiR1325                                                                              XiR278                        __________________________________________________________________________     pJY4285                                                                              ++                                                                               72  ++                                                                                5 ++                                                                               <3 + <3 +  4  - <3 - <3  - <3  -  <3                        (1-115)                                                                        pJY4310                                                                              ++                                                                               116 ++                                                                                4 ++                                                                               <3 +  5 ++                                                                               16  - 31 - #3  - <3  -  <3                        (1-192)                                                                        pJY4306                                                                              ++                                                                               1127                                                                               ++                                                                               78 ++                                                                               554                                                                               ++                                                                               805                                                                               ++                                                                               2614                                                                               ++                                                                               <3 ++                                                                               643 ++                                                                               717 +  <3                        (1-260)                                                                        pBC207                                                                               - <3  - <3 - <3 - <3 + <3  ++                                                                               61 ++                                                                               <3  ++                                                                               <3  ++                                                                               4527                       (119-588)                                                                      PBC100                                                                               - <3  - <3 - <3 - <3 - <3  ++                                                                               15 ++                                                                               709 ++                                                                               4401                                                                               ++                                                                               4746                       (192-588)                                                                      Rx1   ++                                                                               63  ++                                                                               15 ++                                                                               42 ++                                                                               48 ++                                                                               118 ++                                                                               44 ++                                                                               64  ++                                                                               111 ++                                                                                468                       (1-588)                                                                        pIN-III                                                                              - <3  - <3 - <3 - <3 - <3  - <3 - <3  - <3  -  <3                        (none)                                                                         __________________________________________________________________________      .sup.1 Antibodies were reacted with the indicated PspA fragments in            immunoblot of SDSPAGE separations, or by ELISA using microtitration plate      coated with preparations enriched for the indicated PspA fragments. Rx1        PspA serves as a positive control, and pINIII-ompA (vector alone) serves       as a negative control. The results of the immunoblot are presented as ++       (strong reaction). + (weak but clearly positive  #  reaction) and - (no        reaction). ELISA values are given as the reciprocal dilution of each           monoclonal antibody that gave 30% of maximum binding with wells coated         with the indicate fragment preparation.                                        .sup.(2) Plasmids are listed that encode PspA fragments with amino acid        residues shown in parenthesis.                                           

The deduced locations of the epitopes are indicated in FIG. 4.

As can be seen from the data in Table VI, three of the antibodies, Xi126 and XiR35 and XiR1526, react strongly with all three C-terminal-deleted clones in immunoblot analysis (FIG. 5), indicating that the sequence required to form the epitope(s) detected by all three lies within the first 115 amino acids of PspA. This map position is in agreement with the failure of these antibodies to react with either of the N-terminal-deleted clones that lack the first 119 and 191 amino acids.

MAb XiR1224 reacted strongly by immunoblot with the longest C-terminal-deleted fragment (pJY4306), but showed substantially weaker reactions with the shorter two C-terminal-deleted fragments. This result indicates that, while the binding site of the antibody may be in the first 115 amino acids, residues beyond amino acid 192 may be important for the conformation or stability of the epitope.

By immunblot, the three antibodies Xi64, XiR1325 and XiR278, all reacted with the longest C-terminal-deleted fragment and both of the N-terminal-deleted fragments, thus locating their determinants between amino acid positions 192 and 260. Generally confirmatory results were obtained in ELISAs with the native molecules, as described above. However, in a few cases, reactions were observed in ELISAs with full length PspA but not with a truncated molecule even though the same truncated fragment was reactive with the antibody by immunoblot. These observations may have resulted from an altered conformation of the truncated fragments under physiologic conditions that masked or prevented the formation of determinant present in full-length PspA and in the denatured fragments.

Two antibodies, XiR216 and XiR1323, showed what, at first appeared to be anomalous reactions, indicating that epitopes detected by the antibodies might be in more than one portion of PspA. In view of this unexpected result, the assays were repeated multiple times with two sets of preparations of the truncated fragments. The results of the additional assays confirmed the two-position mapping of epitopes for these two MAbs. The data presented in Table VI represents the consensus results of these multiple repeated assays.

By immunoblot, MAb XiR16 reacted strongly with the two longest C-terminal-deleted fragments and failed to react with the shortest N-terminal-deleted fragment. Accordingly, the epitope detected must be N-terminal to position 192. Unexpectedly, MAb XiR16 reacted weakly in immunoblots with both the longest N-terminal-deleted fragment (residues 119 to 158) and the shortest C-terminal-deleted fragment (residues 1 to 115). Since the fragments do not overlap, and if the weak immunoblot reactivities with fragments (reactivities not seen by ELISA) are not an artifact, the MAb XiR16 must recognize epitopes on both fragments.

In the case of MAb XiR1323, the immunoblot data clearly places the detected epitope between positions 192 and 260. In the ELISA studies, however, XiR1323 reacted strongly and reproducibly with the C-terminal-deleted fragment pJY4310 (amino acid residues 1 to 192) as well as the shortest N-terminal-deleted fragment pBC100 (amino acid residues 192 to 588). Curiously, an ELISA reaction was not observed between MAb XiR1323 and pJY4306 (amino acid residues 1 to 260), even though MAb XiR1323 reacted strongly with this fragment by immunoblot.

These findings provide additional evidence for distal conformation effects on antigenic determinants of PspA. They also indicate that, on the native fragments, MAb XiR1323 sees epitopes on both sides of position 192. The relationship between expression of the epitopes in other PspAs and their position in R×1 PspA is demonstrated in Table VI in which is listed the antibodies in accordance with their apparent map position in PspA. The five antibodies (including XiR16) that clearly recognize epitopes N-terminal to position 116 are listed at the left side of Table VI. The four antibodies that clearly recognize epitopes C-terminal to position 192 are listed on the right side of Table VI. Three of the five epitopes N-terminal of position 192 (those recognized by XiR1526, XiR35, and XiR16) were not found on any of the other eight PspAs tested. One epitope (recognized by XiR 1224) was weakly expressed by one other strain and another (recognized by Xi126) was expressed on two other strains. In contrast, the four epitopes present in the C-terminal third of the PspA α-helical region were each present in from two to six other strains. The greater conservation of the region C-terminal to position 192, as compared to the region N-terminal to position 192 was significant at P<0.05 by both the Chi-square and the two sample rank tests. Based on the mapping results (Table IV) and the strain distribution results (Table VI), it is apparent that all of the antibodies except possibly XiR35 and XiR1526 must recognize different PspA determinants.

Example 7

This Example contains a discussion of the mapping results achieved in Example 6.

The results set forth in Example 6 clearly demonstrate that the protection eliciting epitopes of PspA are not restricted to the N-terminal end of the surface exposed α-helical half of the molecule. In fact, four of the five antibodies protective against S. pneumoniae WU2 reacted with the C-terminal third of the α-helical region of PspA. This portion of the α-helical region is thought to closest to the cell wall (see Yother et al (II)).

Five of the nine MAbs recognized determinants N-terminal to amino acid 115 and the other half recognized epitopes C-terminal to residue 192. Since the nine antibodies were selected for their ability to bind native PspA on the surface of heat-killed whole pneumococci, the distribution of the epitopes they recognize suggests that determinants between positions 115 and 192 are either not immunogenic or are not exposed on the native molecule as expressed on pneumococci.

Two MAbs (XiR16 and XiR1323) appeared to possibly react with epitopes in more than one position on PspA. Although the bulk of the data for XiR16 placed its epitope N-terminal of position 115, weak immunoblot patterns suggested that a reactive epitope(s) may also exist C-terminal to residue 115. In the case of XiR1323, the bulk of the data indicated that its epitope is between positions 192 and 260. However, the ELISA assay showed significant reactivity of the antibody with a C-terminal-deleted PspA fragment extending from residues 1 to 192. In the case of XiR1323, the antibody reacted with the epitope on the 1 to 192 fragment under natured but not denatured conditions. This may indicate that the epitope is conformational and may not have the same exact sequence as the epitope recognized (under both natured and denatured conditions) between residues 192 and 260. Although there are no extensive repeats in the N-terminal half of PspA, there are a few short repeated sequences that occur more than once in the coiled-coil motif. One such sequence is glu-glu-ala-lys which starts at amino acid positions 105, 133, and 147 and another is lys-ala-lys-leu starting at positions 150 and 220 (see FIG. 1).

One mechanism that may account for the lack of exposure of epitopes between amino acid 115 and 192 would be a folding back of this portion of the α-helical sequence on itself or other parts of PspA to form a coiled-coil structure more complex than a simple coiled-coil dimer. If this occurred, it could explain how PspA tertiary structure can sometimes be dependent on distant PspA structures. A suggestion that this might, in fact, be the case comes from the observation that some of the truncated forms did not express certain epitopes under physiologic conditions that were detected on the whole molecule under the same conditions and were shown to be present in the fragment after denaturation in SDS.

The presence of protection-eliciting epitopes C-terminal of residue 192 was confirmed by immunizing mice with the PspA fragments produced by pBC100 (amino acids 192 to 588) and pBAR416 (amino acids 192 to 299) (see Example 8 below). The protection elicited by the 192 to 588 fragment made it clear that there were protection-eliciting epitopes C-terminal of amino acid 192. The protection-elicited by fragment 192 to 299 demonstrated that there were protection-eliciting epitope(s) within this portion of the α-helical region.

Since a PspA vaccine may need to contain fragments of several serologically different PspAs, it would be desirable to include in a vaccine only those portions of each PspA that are most likely to elicit cross-protective antibodies. Based on the results presented herein with R×1 PspA, it appears likely that the portion of the PspA sequences corresponding to residues 192 to 260 of R×1 PspA is the best portion of PspA to include in a recombinant PspA vaccine. The epitopes in this portion of PspA were three and a half times as likely to be present in the PspAs of other strains as the epitopes in the residue 1 to 115 portion of the sequence, and none of the 9 antibodies studied clearly reacted with the middle third of the α-helical region.

Example 8

This Example shows cross-protection of an animal model against challenge by a variety of virulent pneumococcal strains by recombinant PspA fragments.

Five mice were immunized with purified PspA fragment produced by pBC207 (produced as described in Example 3) in E. coli, and five with PspA purified fragment produced by pBC100 (produced as described in Example 3) in E. coli. In both cases, the fragments were injected in Freund's Complete Adjuvant, boosted two weeks later with the fragment in saline and challenged 7 days post boost. All mice immunized with each fragment survived challenge with 100×LD₅₀ of WU2 capsular type 3 S. pneumoniae.

Five additional control mice were injected with adjuvant plus an equivalent preparation of non-PspA producing E. coli (KSD1500--DH1 containing plasmid vector but no insert). All mice died when challenged with the same dose of WU2 strain. These results are consistent with the mapping data since the fragments contained the 192 to 260 region.

Further, additional mice were immunized with a purified PspA fragment (pBAR 416) produced by E. coli and corresponding to amino acids 192 to 299, following the protocol described above and challenged with various strains of S. pneumoniae against which protection was provided by the pBC100-derived fragment. The mice immunized with the PspA fragment exhibited an anti-PspA titre of 1/750 by ELISA. Control mice immunized with an osmotic shock preparation from KSD1500 had an anti-PspA titre of <1/10.

The results obtained are contained in the following Table VII:

                  TABLE VII                                                        ______________________________________                                         Protection Mediated by Recombinant pBAR416                                     (amino acids 192-299) PspA from strain Rx1                                                             Median Day of                                                       Alive:Dead Death                                                  Challenge                                                                              Serotype   BAR416         BAR416                                       strain  Caps   PspA    (rPspA)                                                                               none  (rPspA)                                                                               none                                ______________________________________                                         WU2     3      1       4:1    0:4   >21    3                                   A66     3      13      5:0    0:5   >21    2                                   BG7322  6B     24      3:2    0:4   >21    7                                   ATCC6303                                                                               3      7       2:3    1:4   13     4                                   EF6796  6A     1       3:2    0:5   >21    5                                   DBL6A   6A     19      0:5    0:5   7      2                                   ______________________________________                                          The strains tested are all strains protected against by immunization with      BC100. The results indicate that the region from 192-260 is able to elici      much of the crossprotection elicited by BC100.                                 Infected with ≧100 × LD.sub.50 of each strain. In all cases       this is ≧10.sup.3 CFU.                                            

As may be seen from this Table VII, protection was afforded against challenge in many instances and in others the life was extended.

In addition, further numbers of mice were immunized with purified fragment produced by pBC100 in E. coli following the protocol described above. The mice were challenged with a variety of virulent strains and the pBC100 fragment was found to protect mice against 7 of 14 virulent strains and to extend life for the other 7 strains. The results obtained, which includes the result for the WU2 challenge, are set forth in the following Table VIII:

                  TABLE VIII                                                       ______________________________________                                         Protection Mediated by Recombinant (BC100)                                     (amino acids 192-588) PspA from strain Rx1                                                             Median Day of                                                       Alive:Dead Death                                                  Challenge                                                                              Serotype   BC100          BC100                                        strain  Caps   PspA    (rPspA)                                                                               none  (rPspA)                                                                               none                                ______________________________________                                         D39     2      25      0:5    0:3   5      2                                   WU2     3      1       4:0    0:3   >21*   3                                   A66     3      13      4:0    0:3   >21*   1                                   EF10197 3      18      5:0    0:3   >21*   2                                   ATCC6303                                                                               3      7       5:0    0:5   >21**  5                                   EF5668  4      12      1:3    0:3     9.5  4                                   EF3296  4      20      1:3    0:3   5      3                                   L81905  4      23      1:5    0:6    5*    2.5                                 BC9739  4      26      0:4    0:3   7      2                                   DBL5    5      33      0:5    0:3    5*    2                                   BG7322  6      24      4:0    1:3   >21*   6                                   EF6796  6A     1       4:0    0:3   >21*   1                                   DBL6A   6A     19      5:0    0:3   >21*   7                                   ______________________________________                                          *, different from "none" at P ≦ .004 in one tailed tests,               **, different from "none" at P ≦ .05 one tailed tests, all are          Fisher exact except DBL5 and L81905 where the one tailed two sample rank       test was used.                                                           

The data presented in this Example conclusively proves that epitopes C-terminal to amino acids 119 and 192 respectively are capable of eliciting protective immunity. This result is consistent with the findings presented in the earlier Examples from epitope mapping that the region of PspA from amino acids 192 to 260 contains at least one protection-eliciting epitope.

Example 9

This Example shows cross-protection of an animal model against challenge by a C-terminal fragment of PspA including only proline and repeat regions.

Mice were immunized with purified PspA fragment produced by pBAR501 (produced as described in Example 3) in E. coli using the protocol set forth in Example 8. Control mice were immunized with an identical preparation that did not contain any PspA. Both groups of mice were challenged with approximately 100×LD₅₀ of various strains of S. pneumoniae.

The results obtained are shown in the following Table IX:

                  TABLE IX                                                         ______________________________________                                         Cross-protection of mice immunized with BAR501                                 (proline/repeats region).sup.a                                                                          PspA.sup.-                                                                             PspA.sup.+                                    Challenge                                                                             Capsular PspA     # of mice                                                                              # of mice                                     Strain Serotype Serotype alive/# dead                                                                           alive/# dead                                                                           P value                               ______________________________________                                         WU2    3        1         0/10   10/0    <0.0001                               A66    3        13       0/5     5/0     <0.008                                DBL6A  6A       19       0/5     5/0     <0.008                                EF6796 6A       1        1/5     1/4     N.S.                                  ______________________________________                                          .sup.a. Mice were immunized with BAR501 or an identical preparation that       did not contain any PspA. They were challenged with approximately 100          × LD.sub.50 of the indicated strains.                              

The data seen in Table IX shows that the C-terminal PspA fragment produced by pBAR501 confers cross-protection against a variety of virulent pneumococcal strains.

Example 10

This Example shows the cross-protection of an animal model against challenge by a variety of pneumococcal strains by whole-length recombinant PspA's.

Five mice were immunized with purified whole length recombinant PspAs from the R×1 and EF5668 strains of Streptococcus pneumoniae, expressed in E. coli. The PspA was injected subcutaneously in Freund's complete adjuvant, boosted two weeks later with the whole length PspA in incomplete Freund's adjuvant, and challenged intravenously 7 days post boost, with 100×LD₅₀ of the virulent strain.

The results obtained are shown in the following Tables X and XI:

                  TABLE X                                                          ______________________________________                                         Protection Against Streptococcus pneumoniae Isolates By                        Immunization with Rx1 or EF5666 PspA                                                        Immunizing PspA                                                                (++ = protected                                                                + = extended life                                                                              Best of                                                        0 = little effect)                                                                             Rx1                                               Challenge                                                                              Serotype   Rx1*       EF5668   or                                      Strains Capsule PspA   PspA type 25                                                                            PspA type 12                                                                            EFS668                                ______________________________________                                         WU2     3        1     ++       ++       ++                                    A66     3       13     ++       ++       ++                                    EF10197 3       18     ++                ++                                    ATCC6303                                                                               3        7     ++                ++                                    BG9739  4       26     +                 +                                     EF3296  4       20     +/0               +/0                                   L81905  4       23     +                 +                                     EF5668  4       12     +        ++       ++                                    EF6796  6A       1     ++       ++       ++                                    DBL6A   6A      19     ++                ++                                    GB9163  6B      21     ++                ++                                    BG7322  6B      24     ++       ++       ++                                    DBL5    5       33     +                 +                                     D39     2       25     ++/+/0.sup.a                                                                            +        ++/+/0.sup.a                          Proportion of Strains                                                                         57%                   64%                                       Protected Against Fatal                                                        Infection                                                                      ______________________________________                                          *The Rx1 data represents pooled results form immunization with fulllength      and fragments of Rx1 PspA.                                                     .sup.a Protection against death was observed but only with 10x more Ab         than was required than for protection against WU2.                       

                                      TABLE XI                                     __________________________________________________________________________     Protection Mediated by Recombinant full-length PspA from Sttain EF5668         Challenge                                                                           Serologic type                                                                        Alive:Dead                                                                              Median Day of Death                                       strain                                                                              capsule                                                                            PspA                                                                              (rPspA)                                                                            no PspA                                                                             (rPspA)                                                                             no PspA                                                                             P value                                         __________________________________________________________________________     WU2  3    1 8:0 0:7  >10  2    <0.001                                          A66  3   13 4:1 0:4  >10    2.5                                                                               <0.05                                           EF5668                                                                              4   12 5:0 1:4  >10  2    <0.01                                           BG7322                                                                              6   24 5:1 1:5  >10  7    <0.025                                          D39  2   25 3:2 0:5  >10  3    N.S.                                            __________________________________________________________________________      Challenge was with 1000 CFU in XID mice (in all cases ≧ 100X the        LD.sub.50).                                                              

As may be seen from the Tables X and XI, the PspA from R×1 provided protection against a broad spectrum of S. pneumoniae strains while that from EF5668 also provided cross-protection against a number of strains. These results indicate that a limited number of serological PspA types may elicit protection against a broad spectrum of different pneumococci. This data also substantiates the potential use of PspA as an important component of a protein-based pneumococcal vaccine.

SUMMARY OF THE DISCLOSURE

In summary of this disclosure, the present invention provides PspA protein fragments which contain protection-eliciting epitopes and which are cross-reactive and can be incorporated into a vaccine against disease caused by pneumococcal infection. Modifications are possible within the scope of this invention.

    __________________________________________________________________________     #             SEQUENCE LISTING                                                 - (1) GENERAL INFORMATION:                                                     -    (iii) NUMBER OF SEQUENCES: 20                                             - (2) INFORMATION FOR SEQ ID NO:1:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 2085 base                                                          (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: protein                                              -    (iii) HYPOTHETICAL: NO                                                    -     (iv) ANTI-SENSE: NO                                                      -     (vi) ORIGINAL SOURCE:                                                              (A) ORGANISM: Streptococcu - #s pneumoniae                                     (B) STRAIN: Rx1                                                      -    (vii) IMMEDIATE SOURCE:                                                             (B) CLONE: JY4313                                                    -     (ix) FEATURE:                                                                      (A) NAME/KEY: intron                                                           (B) LOCATION: 1..2085                                                -     (ix) FEATURE:                                                                      (A) NAME/KEY: CDS                                                              (B) LOCATION: join(127..19 - #84)                                    -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                  - AAGCTTATGA TATAGAAATT TGTAACAAAA ATGTAATATA AAACACTTGA CA - #AATATTTA          60                                                                           - CGGAGGAGGC TTATACTTAA TATAAGTATA GTCTGAAAAT GACTATCAGA AA - #AGAGGTAA         120                                                                           #AGT CTA GCC AGC GTC       168TG ATT TTA ACA                                          Met Asn Lys Lys Lys Met Il - #e Leu Thr Ser Leu Ala Ser Val             #      10                                                                      - CCT ATC TTA GGG GCT GGT TTT GTT GCG TCT CA - #G CCT ACT GTT GTA AGA           216                                                                           Ala Ile Leu Gly Ala Gly Phe Val Ala Ser Gl - #n Pro Thr Val Val Arg            # 30                                                                           - GCA GAA GAA TCT CCC GTA GCC AGT CAG TCT AA - #A GCT GAG AAA GAC TAT           264                                                                           Ala Glu Glu Ser Pro Val Ala Ser Gln Ser Ly - #s Ala Glu Lys Asp Tyr            #                 45                                                           - GAT GCA GCG AAG AAA GAT GCT AAG AAT GCG AA - #A AAA GCA GTA GAA GAT           312                                                                           Asp Ala Ala Lys Lys Asp Ala Lys Asn Ala Ly - #s Lys Ala Val Glu Asp            #             60                                                               - GCT CAA AAG GCT TTA GAT GAT GCA AAA GCT GC - #T CAG AAA AAA TAT GAC           360                                                                           Ala Gln Lys Ala Leu Asp Asp Ala Lys Ala Al - #a Gln Lys Lys Tyr Asp            #         75                                                                   - GAG GAT CAG AAG AAA ACT GAG GAG AAA GCC GC - #G CTA GAA AAA GCA GCG           408                                                                           Glu Asp Gln Lys Lys Thr Glu Glu Lys Ala Al - #a Leu Glu Lys Ala Ala            #     90                                                                       - TCT GAA GAG ATG GAT AAG GCA GTG GCA GCA GT - #T CAA CAA GCG TAT CTA           456                                                                           Ser Glu Glu Met Asp Lys Ala Val Ala Ala Va - #l Gln Gln Ala Tyr Leu            #110                                                                           - GCC TAT CAA CAA GCT ACA GAC AAA GCC GCA AA - #A GAC GCA GCA GAT AAG           504                                                                           Ala Tyr Gln Gln Ala Thr Asp Lys Ala Ala Ly - #s Asp Ala Ala Asp Lys            #               125                                                            - ATG ATA GAT GAA GCT AAG AAA CGC GAA GAA GA - #G GCA AAA ACT AAA TTT           552                                                                           Met Ile Asp Glu Ala Lys Lys Arg Glu Glu Gl - #u Ala Lys Thr Lys Phe            #           140                                                                - AAT ACT GTT CGA GCA ATG GTA GTT CCT GAG CC - #A GAG CAG TTG GCT GAG           600                                                                           Asn Thr Val Arg Ala Met Val Val Pro Glu Pr - #o Glu Gln Leu Ala Glu            #       155                                                                    - ACT AAG AAA AAA TCA GAA GAA GCT AAA CAA AA - #A GCA CCA GAA CTT ACT           648                                                                           Thr Lys Lys Lys Ser Glu Glu Ala Lys Gln Ly - #s Ala Pro Glu Leu Thr            #   170                                                                        - AAA AAA CTA GAA GAA GCT AAA GCA AAA TTA GA - #A GAG GCT GAG AAA AAA           696                                                                           Lys Lys Leu Glu Glu Ala Lys Ala Lys Leu Gl - #u Glu Ala Glu Lys Lys            175                 1 - #80                 1 - #85                 1 -        #90                                                                            - GCT ACT GAA GCC AAA CAA AAA GTG GAT GCT GA - #A GAA GTC GCT CCT CAA           744                                                                           Ala Thr Glu Ala Lys Gln Lys Val Asp Ala Gl - #u Glu Val Ala Pro Gln            #               205                                                            - GCT AAA ATC GCT GAA TTG GAA AAT CAA GTT CA - #T AGA CTA GAA CAA GAG           792                                                                           Ala Lys Ile Ala Glu Leu Glu Asn Gln Val Hi - #s Arg Leu Glu Gln Glu            #           220                                                                - CTC AAA GAG ATT GAT GAG TCT GAA TCA GAA GA - #T TAT GCT AAA GAA GGT           840                                                                           Leu Lys Glu Ile Asp Glu Ser Glu Ser Glu As - #p Tyr Ala Lys Glu Gly            #       235                                                                    - TTC CGT GCT CCT CTT CAA TCT AAA TTG GAT GC - #C AAA AAA GCT AAA CTA           888                                                                           Phe Arg Ala Pro Leu Gln Ser Lys Leu Asp Al - #a Lys Lys Ala Lys Leu            #   250                                                                        - TCA AAA CTT GAA GAG TTA AGT GAT AAG ATT GA - #T GAG TTA GAC GCT GAA           936                                                                           Ser Lys Leu Glu Glu Leu Ser Asp Lys Ile As - #p Glu Leu Asp Ala Glu            255                 2 - #60                 2 - #65                 2 -        #70                                                                            - ATT GCA AAA CTT GAA GAT CAA CTT AAA GCT GC - #T GAA GAA AAC AAT AAT           984                                                                           Ile Ala Lys Leu Glu Asp Gln Leu Lys Ala Al - #a Glu Glu Asn Asn Asn            #               285                                                            - GTA GAA GAC TAC TTT AAA GAA GGT TTA GAG AA - #A ACT ATT GCT GCT AAA          1032                                                                           Val Glu Asp Tyr Phe Lys Glu Gly Leu Glu Ly - #s Thr Ile Ala Ala Lys            #           300                                                                - AAA GCT GAA TTA GAA AAA ACT GAA GCT GAC CT - #T AAG AAA GCA GTT AAT          1080                                                                           Lys Ala Glu Leu Glu Lys Thr Glu Ala Asp Le - #u Lys Lys Ala Val Asn            #       315                                                                    - GAG CCA GAA AAA CCA GCT CCA GCT CCA GAA AC - #T CCA GCC CCA GAA GCA          1128                                                                           Glu Pro Glu Lys Pro Ala Pro Ala Pro Glu Th - #r Pro Ala Pro Glu Ala            #   330                                                                        - CCA GCT GAA CAA CCA AAA CCA GCG CCG GCT CC - #T CAA CCA GCT CCC GCA          1176                                                                           Pro Ala Glu Gln Pro Lys Pro Ala Pro Ala Pr - #o Gln Pro Ala Pro Ala            335                 3 - #40                 3 - #45                 3 -        #50                                                                            - CCA AAA CCA GAG AAG CCA GCT GAA CAA CCA AA - #A CCA GAA AAA ACA GAT          1224                                                                           Pro Lys Pro Glu Lys Pro Ala Glu Gln Pro Ly - #s Pro Glu Lys Thr Asp            #               365                                                            - GAT CAA CAA GCT GAA GAA GAC TAT GCT CGT AG - #A TCA GAA GAA GAA TAT          1272                                                                           Asp Gln Gln Ala Glu Glu Asp Tyr Ala Arg Ar - #g Ser Glu Glu Glu Tyr            #           380                                                                - AAT CGC TTG ACT CAA CAG CAA CCG CCA AAA GC - #T GAA AAA CCA GCT CCT          1320                                                                           Asn Arg Leu Thr Gln Gln Gln Pro Pro Lys Al - #a Glu Lys Pro Ala Pro            #       395                                                                    - GCA CCA AAA ACA GGC TGG AAA CAA GAA AAC GG - #T ATG TGG TAC TTC TAC          1368                                                                           Ala Pro Lys Thr Gly Trp Lys Gln Glu Asn Gl - #y Met Trp Tyr Phe Tyr            #   410                                                                        - AAT ACT GAT GGT TCA ATG GCG ACA GGA TGG CT - #C CAA AAC AAC GGT TCA          1416                                                                           Asn Thr Asp Gly Ser Met Ala Thr Gly Trp Le - #u Gln Asn Asn Gly Ser            415                 4 - #20                 4 - #25                 4 -        #30                                                                            - TGG TAC TAC CTC AAC AGC AAT GGT GCT ATG GC - #T ACA GGT TGG CTC CAA          1464                                                                           Trp Tyr Tyr Leu Asn Ser Asn Gly Ala Met Al - #a Thr Gly Trp Leu Gln            #               445                                                            - TAC AAT GGT TCA TGG TAT TAC CTC AAC GCT AA - #C GGC GCT ATG GCA ACA          1512                                                                           Tyr Asn Gly Ser Trp Tyr Tyr Leu Asn Ala As - #n Gly Ala Met Ala Thr            #           460                                                                - GGT TGG GCT AAA GTC AAC GGT TCA TGG TAC TA - #C CTC AAC GCT AAT GGT          1560                                                                           Gly Trp Ala Lys Val Asn Gly Ser Trp Tyr Ty - #r Leu Asn Ala Asn Gly            #       475                                                                    - GCT ATG GCT ACA GGT TGG CTC CAA TAC AAC GG - #T TCA TGG TAT TAC CTC          1608                                                                           Ala Met Ala Thr Gly Trp Leu Gln Tyr Asn Gl - #y Ser Trp Tyr Tyr Leu            #   490                                                                        - AAC GCT AAC GGC GCT ATG GCA ACA GGT TGG GC - #T AAA GTC AAC GGT TCA          1656                                                                           Asn Ala Asn Gly Ala Met Ala Thr Gly Trp Al - #a Lys Val Asn Gly Ser            495                 5 - #00                 5 - #05                 5 -        #10                                                                            - TGG TAC TAC CTC AAC GCT AAT GGT GCT ATG GC - #T ACA GGT TGG CTC CAA          1704                                                                           Trp Tyr Tyr Leu Asn Ala Asn Gly Ala Met Al - #a Thr Gly Trp Leu Gln            #               525                                                            - TAC AAC GGT TCA TGG TAC TAC CTC AAC GCT AA - #C GGT GCT ATG GCT ACA          1752                                                                           Tyr Asn Gly Ser Trp Tyr Tyr Leu Asn Ala As - #n Gly Ala Met Ala Thr            #           540                                                                - GGT TGG GCT AAA GTC AAC GGT TCA TGG TAC TA - #C CTC AAC GCT AAT GGT          1800                                                                           Gly Trp Ala Lys Val Asn Gly Ser Trp Tyr Ty - #r Leu Asn Ala Asn Gly            #       555                                                                    - GCT ATG GCA ACA GGT TGG GTG AAA GAT GGA GA - #T ACC TGG TAC TAT CTT          1848                                                                           Ala Met Ala Thr Gly Trp Val Lys Asp Gly As - #p Thr Trp Tyr Tyr Leu            #   570                                                                        - GAA GCA TCA GGT GCT ATG AAA GCA AGC CAA TG - #G TTC AAA GTA TCA GAT          1896                                                                           Glu Ala Ser Gly Ala Met Lys Ala Ser Gln Tr - #p Phe Lys Val Ser Asp            575                 5 - #80                 5 - #85                 5 -        #90                                                                            - AAA TGG TAC TAT GTC AAT GGT TTA GGT GCC CT - #T GCA GTC AAC ACA ACT          1944                                                                           Lys Trp Tyr Tyr Val Asn Gly Leu Gly Ala Le - #u Ala Val Asn Thr Thr            #               605                                                            - GTA GAT GGC TAT AAA GTC AAT GCC AAT GGT GA - #A TGG GTT TAA GCC GAT          1992                                                                           Val Asp Gly Tyr Lys Val Asn Ala Asn Gly Gl - #u Trp Val  *                     #           615                                                                - TAA ATT AAA GCA TGT TAA GAA CAT TTG ACA TT - #T TAA TTT TGA AAC AAA          2040                                                                           GAT AAG GTT CGA TTG AAT AGA TTT ATG TTC GT - #A TTC TTT AGG TAC                2085                                                                           - (2) INFORMATION FOR SEQ ID NO:2:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 619 amino                                                          (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: protein                                              -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                  - Met Asn Lys Lys Lys Met Ile Leu Thr Ser Le - #u Ala Ser Val Ala Ile          #                 15                                                           - Leu Gly Ala Gly Phe Val Ala Ser Gln Pro Th - #r Val Val Arg Ala Glu          #             30                                                               - Glu Ser Pro Val Ala Ser Gln Ser Lys Ala Gl - #u Lys Asp Tyr Asp Ala          #         45                                                                   - Ala Lys Lys Asp Ala Lys Asn Ala Lys Lys Al - #a Val Glu Asp Ala Gln          #     60                                                                       - Lys Ala Leu Asp Asp Ala Lys Ala Ala Gln Ly - #s Lys Tyr Asp Glu Asp          # 80                                                                           - Gln Lys Lys Thr Glu Glu Lys Ala Ala Leu Gl - #u Lys Ala Ala Ser Glu          #                 95                                                           - Glu Met Asp Lys Ala Val Ala Ala Val Gln Gl - #n Ala Tyr Leu Ala Tyr          #           110                                                                - Gln Gln Ala Thr Asp Lys Ala Ala Lys Asp Al - #a Ala Asp Lys Met Ile          #       125                                                                    - Asp Glu Ala Lys Lys Arg Glu Glu Glu Ala Ly - #s Thr Lys Phe Asn Thr          #   140                                                                        - Val Arg Ala Met Val Val Pro Glu Pro Glu Gl - #n Leu Ala Glu Thr Lys          145                 1 - #50                 1 - #55                 1 -        #60                                                                            - Lys Lys Ser Glu Glu Ala Lys Gln Lys Ala Pr - #o Glu Leu Thr Lys Lys          #               175                                                            - Leu Glu Glu Ala Lys Ala Lys Leu Glu Glu Al - #a Glu Lys Lys Ala Thr          #           190                                                                - Glu Ala Lys Gln Lys Val Asp Ala Glu Glu Va - #l Ala Pro Gln Ala Lys          #       205                                                                    - Ile Ala Glu Leu Glu Asn Gln Val His Arg Le - #u Glu Gln Glu Leu Lys          #   220                                                                        - Glu Ile Asp Glu Ser Glu Ser Glu Asp Tyr Al - #a Lys Glu Gly Phe Arg          225                 2 - #30                 2 - #35                 2 -        #40                                                                            - Ala Pro Leu Gln Ser Lys Leu Asp Ala Lys Ly - #s Ala Lys Leu Ser Lys          #               255                                                            - Leu Glu Glu Leu Ser Asp Lys Ile Asp Glu Le - #u Asp Ala Glu Ile Ala          #           270                                                                - Lys Leu Glu Asp Gln Leu Lys Ala Ala Glu Gl - #u Asn Asn Asn Val Glu          #       285                                                                    - Asp Tyr Phe Lys Glu Gly Leu Glu Lys Thr Il - #e Ala Ala Lys Lys Ala          #   300                                                                        - Glu Leu Glu Lys Thr Glu Ala Asp Leu Lys Ly - #s Ala Val Asn Glu Pro          305                 3 - #10                 3 - #15                 3 -        #20                                                                            - Glu Lys Pro Ala Pro Ala Pro Glu Thr Pro Al - #a Pro Glu Ala Pro Ala          #               335                                                            - Glu Gln Pro Lys Pro Ala Pro Ala Pro Gln Pr - #o Ala Pro Ala Pro Lys          #           350                                                                - Pro Glu Lys Pro Ala Glu Gln Pro Lys Pro Gl - #u Lys Thr Asp Asp Gln          #       365                                                                    - Gln Ala Glu Glu Asp Tyr Ala Arg Arg Ser Gl - #u Glu Glu Tyr Asn Arg          #   380                                                                        - Leu Thr Gln Gln Gln Pro Pro Lys Ala Glu Ly - #s Pro Ala Pro Ala Pro          385                 3 - #90                 3 - #95                 4 -        #00                                                                            - Lys Thr Gly Trp Lys Gln Glu Asn Gly Met Tr - #p Tyr Phe Tyr Asn Thr          #               415                                                            - Asp Gly Ser Met Ala Thr Gly Trp Leu Gln As - #n Asn Gly Ser Trp Tyr          #           430                                                                - Tyr Leu Asn Ser Asn Gly Ala Met Ala Thr Gl - #y Trp Leu Gln Tyr Asn          #       445                                                                    - Gly Ser Trp Tyr Tyr Leu Asn Ala Asn Gly Al - #a Met Ala Thr Gly Trp          #   460                                                                        - Ala Lys Val Asn Gly Ser Trp Tyr Tyr Leu As - #n Ala Asn Gly Ala Met          465                 4 - #70                 4 - #75                 4 -        #80                                                                            - Ala Thr Gly Trp Leu Gln Tyr Asn Gly Ser Tr - #p Tyr Tyr Leu Asn Ala          #               495                                                            - Asn Gly Ala Met Ala Thr Gly Trp Ala Lys Va - #l Asn Gly Ser Trp Tyr          #           510                                                                - Tyr Leu Asn Ala Asn Gly Ala Met Ala Thr Gl - #y Trp Leu Gln Tyr Asn          #       525                                                                    - Gly Ser Trp Tyr Tyr Leu Asn Ala Asn Gly Al - #a Met Ala Thr Gly Trp          #   540                                                                        - Ala Lys Val Asn Gly Ser Trp Tyr Tyr Leu As - #n Ala Asn Gly Ala Met          545                 5 - #50                 5 - #55                 5 -        #60                                                                            - Ala Thr Gly Trp Val Lys Asp Gly Asp Thr Tr - #p Tyr Tyr Leu Glu Ala          #               575                                                            - Ser Gly Ala Met Lys Ala Ser Gln Trp Phe Ly - #s Val Ser Asp Lys Trp          #           590                                                                - Tyr Tyr Val Asn Gly Leu Gly Ala Leu Ala Va - #l Asn Thr Thr Val Asp          #       605                                                                    - Gly Tyr Lys Val Asn Ala Asn Gly Glu Trp Va - #l                              #   615                                                                        - (2) INFORMATION FOR SEQ ID NO:3:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 26 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                                  #              26  CACC AAAAAC                                                 - (2) INFORMATION FOR SEQ ID NO:4:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 33 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:                                  #         33       AACC CATTCACCAT TGG                                         - (2) INFORMATION FOR SEQ ID NO:5:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 28 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:                                  #             28   AGCA GTTGGCTG                                               - (2) INFORMATION FOR SEQ ID NO:6:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 31 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:                                  #          31      AGAT TGATGAGTCT G                                           - (2) INFORMATION FOR SEQ ID NO:7:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 31 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:                                  #          31      GTCA GTCTAAAGCT G                                           - (2) INFORMATION FOR SEQ ID NO:8:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 31 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:                                  #          31      TTCT GGAGCTGGAG C                                           - (2) INFORMATION FOR SEQ ID NO:9:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 31 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9:                                  #          31      CTCC AGAAACTCCA G                                           - (2) INFORMATION FOR SEQ ID NO:10:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 32 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10:                                 #          32      TATT TACGGAGGAG GC                                          - (2) INFORMATION FOR SEQ ID NO:11:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 20 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11:                                 # 20               CTGG                                                        - (2) INFORMATION FOR SEQ ID NO:12:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 17 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:12:                                 #   17             G                                                           - (2) INFORMATION FOR SEQ ID NO:13:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 17 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:13:                                 #   17             C                                                           - (2) INFORMATION FOR SEQ ID NO:14:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 33 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:14:                                 #         33       TATC TTAGGGGCTG GTT                                         - (2) INFORMATION FOR SEQ ID NO:15:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 28 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:15:                                 #             28   GAAA TTTGTAAC                                               - (2) INFORMATION FOR SEQ ID NO:16:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 30 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:16:                                 #           30     TCTT GTTCTAGTCT                                             - (2) INFORMATION FOR SEQ ID NO:17:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 27 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:17:                                 #             27   TCTT GTTCTAG                                                - (2) INFORMATION FOR SEQ ID NO:18:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 27 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:18:                                 #             27   TTAA CTGCTTT                                                - (2) INFORMATION FOR SEQ ID NO:19:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 31 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:19:                                 #          31      GTCA GTCTAAAGCT G                                           - (2) INFORMATION FOR SEQ ID NO:20:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 35 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:20:                                 #       35         ACCA CTTACCCTTA AGGCG                                       __________________________________________________________________________ 

What we claim is:
 1. An isolated, truncated pneumococcal surface protein A (PspA) fragment comprising amino acid residues 293 to 588 or 268 to 588 of PspA of Streptococcus pneumoniae and containing at least one protection-eliciting epitope.
 2. An isolated polypeptide comprising at least one protection-eliciting epitope contained in amino acid residues 268 to 588 of pneumococcal surface protein A (PspA) of Streptococcus pneumoniae.
 3. An isolated polypeptide comprising at least one protection-eliciting epitope contained in amino acid residues 293 to 588 of pneumococcal surface protein A (PspA) of Streptococcus pneumoniae.
 4. The fragment of claim 1 which is produced recombinantly.
 5. The polypeptide of claim 2 which is produced recombinantly.
 6. The polypeptide of claim 3 which is produced recombinantly.
 7. The isolated pneumococcal surface protein A (PspA) fragment as claimed in claim 1 comprising amino acid residues 293 to 588 of PspA.
 8. The isolated pneumococcal surface protein A (PspA) fragment as claimed in claim 1 comprising amino acid residues 268 to 588 of PspA.
 9. An immunological composition comprising the PspA fragment or the polypeptide of any one of claims 2-8 and a suitable carrier or diluent.
 10. A method for eliciting an immunological response in a host comprising administering the immunological composition of claim
 9. 